Consumers in California and Florida are seeking class-action status for their lawsuits that accuse a large New England dairy cooperative of selling "fake" Greek yogurt.

Plaintiffs in the complaints -- Timothy Smith of Berkeley, Calif., and Cynthia Long of Tamarac, Fla. -- allege the Agri-Mark cooperative and its Cabot Creamery subsidiary sold inauthentic Greek yogurt.

Manufacturing Greek yogurt is a "relatively expensive" process that involves straining the solids from fermented milk to create a "thick protein-packed yogurt with the consistency like sour cream," one complaint said.

Producing a gallon of Greek yogurt requires four times as much milk as regular yogurt, the complaint said.

The complaint contends that the fillers are additives not approved by the U.S. Food and Drug Administration, which renders the product adulterated and non-salable in the U.S.

Both lawsuits request certification as class actions, which means other consumers of Cabot Greek yogurt would be included in the litigation.

The complaints seek more than $5 million in compensation and damages, with the exact amount to be determined in court.

Doug DiMento, spokesman for Agri-Mark and Cabot, said the cooperative expects to defend itself vigorously in the litigation.

"We believe the complaint is entirely without merit," he said.

The company doesn't deny using whey protein concentrate and milk protein concentrate in its product, but DiMento disputed that these substances were cheap fillers.

"Nothing could be further from the truth," he said, noting that they were actually fairly expensive ingredients. "No one method is correct and no one method is specified in federal regulations."

Corey Henry, spokesman for the National Yogurt Association, said the FDA has proposed regulations for what constitutes yogurt and what ingredients can be used in it, but these rules haven't yet been finalized.

"At the moment, there is no standard of identity for the entire yogurt category, including Greek yogurt," he said.

Manufacturers have differing opinions about what can be put in yogurt, but whey protein concentrate and milk protein concentrate are "generally recognized as safe" ingredients by the FDA, Henry said.